i:;i; 



THE VOYAGE OF H.M.S. CHALLENGER. 



to science. They may be distinguished by characters taken from the branchial sac alone, 

 as shown by the following table : — 



Cynthia. 



Branchial sac with 6 folds 

 upon each side. 



! 



S or 9 internal longitudinal 5 or 6 internal longitudinal 

 bars upon a fold. bars upon a fold. 



| 



9 or 10 stigmata 



in a mesh. 



I . 

 Cynthia 



formosa. 



6 stigmata 

 in a mesh. 



! 



Cynthia 

 cerebriformis. 



Branchial sac with more than 

 6 folds upon each side. 



with with with with 



7 folds. 8 folds. 9 folds. 11 folds. 



I I I 



Cynthia Cynthia Cynthia 



pallida, hispida. complanata. 



About 9 internal 



longitudinal bars 



on a fold. 



6 to 8 stigmata 

 in a mesh. 



I 

 Cynthia fissa. 



4 stigmata Cynthia 

 in a mesh, irregularis. 



Cynthia arenosa. 



About 4 internal 



longitudinal bars 



on a fold. 



I 

 Cynthia 



papietensis. 



Cynthia cerebriformis, Herdman (PL XV. figs. 5-7). 



Cynthia cerebriformis, Herdman, Prelim. Rep., Proc. Roy. Soc. Edin., 1880-81, p. 57. 



External Appearance. — The -body is irregularly pyriform; the anterior end is wide 

 and is bent over greatly to the right side, which is concave, while the left is prominent 

 and convex. The posterior end is drawn out into a short stalk, tapering towards the point 

 of attachment. The apertures are not distant, both are terminal, and placed at the anterior 

 edge of the right side, slightly projecting, and directed to the right and a little anteriorly. 

 The surface is suleated all over, so as to closely resemble the convoluted surface of a 

 brain ; four large convolutions lead up to each aperture. The posterior end and the stalk 

 are wrinkled, but not sidcated like the rest. The colour is dirty yellowish-white, becom- 

 ing brown on the stalk. 



Length of the body, 6 "5 cm.; breadth of the body, 4 - 7 cm. 



The Test is thick, and very stiff and solid ; it is white on section and on the inner 

 surface. 



The Mantle is very thick, and is muscular at the anterior end. The branchial 

 siphon is short and wide ; the atrial is narrower, but nearly twice as long. 



The Branchial Sac has six folds on each side. The internal longitudinal bars are 

 numerous, there are about nine on a fold, and the same number in the interspace. The 

 transverse vessels are all of the same size. The meshes are occasionally divided by 

 narrow horizontal membranes, and contain each six stigmata. 



